Hurricane Energy's said its 300m barrel estimate from its Lancaster field is now thought to be too conservative.
The oil company said it expects a "material uplift" in anticipated reserves ahead of a competent persons report (CPR) which will quantify the resources at the end of the first quarter.
Shares increased more than three per cent at the market open.
The updated data reinforces the company's pre-drill estimates that the field is substantial relative to both North Sea and European discoveries.
Hurricane previously reported a flow rate of at least 14,500 barrels per day (bpd) in its Lancaster well, which has now been adjusted to a maximum stable rate of 15,375 bpd, following third party interpretation of the flow meter data.
The Lancaster well also goes deeper than previous estimates showed, with an oil-water contact level of 1,678 metres instead of 1,620 metres. Lancaster’s oil column is now said to be in excess of 670 metres, the statement said.
Dr Robert Trice, chief executive of Hurricane, said the new data reinforces the company's belief that its Lancaster field is substantial.
In December, Hurricane Energy's share price stormed more than 13 per cent higher after the group announced it had made a "significant" find at its North Sea Lincoln well.